I have been always curious on how these IM’s work. My favourite IM being MSN Messenger. I was searching for documentation and code-snippets to understand on what goes back and forth over the wire when we use Messenger. I came across the following
The official documentation from Microsoft for Windows Messenger (the poor cousin of MSN Messenger) is found here. This lists the Messenger Client APIs, the Service APIs and more. Though not updated recently it is the only official source.
The most active, single source of information about MSN Messenger is the site appropriately called MSNFanatics. The site has discussion forums about the Messenger API, security concerns, add-ons and more. Recently it has a tool called TabMgr that allows you to write your own Tabs in MSN Messenger.
The website that I found with well written documentation and example sessions for a developer is from Mike Mintz. Check this out at http://www.hypothetic.org/docs/msn/index.php, you will love it.
If you like Java (I like the coffee) then you can get the JMSN client source from Sourceforge, that shows a working Java client that uses MSN Messenger protocol.
As usual, this post comes with the disclaimer that I don’t support or endorse in any way, any of the above sites and you are on your own; your individual mileages may vary :-) . MSN, MSN Messenger are copyright and/or Trademark of Microsoft Corporation.